The present invention relates to an optical fiber cable which comprises a fiber having a central core and a surrounding cladding and which fiber cable is made for transmitting high optical power, specifically power exceeding 1 kW. At least one of the contact ends of the fiber has cooling means for optical power loss.
Optical fiber cables for transmitting high optical power are frequently used in industrial applications. Specifically they are used in cutting and welding operations by means of high-power laser radiation, but also in other industrial applications such as heating, detection or working operations in high-temperature environments this type of optical fiber cables can be used. One of the main problems in this type of high power applications, however, is the problem how to take care of radiation that falls outside the core of the fiber. The power density is normally very high and specific cooling means are required in order to prevent an uncontrolled heating, especially in case of strong back scattering in for instance welding operations.
Different methods to take care of such undesired power radiation are already known. One example is disclosed in DE 4305313, in which the radiation that falls into the cladding of the fiber is spread in a so-called mode stripper and absorbed by a metal surface. This surface can then be cooled from the outside of the component. A similar method is described in SE 83.07140-7.
An optical fiber cable of the above-mentioned type is also presented in SE 93.01100-5. In said fiber cable at least one of the end surfaces of the fiber core is provided with a rod having a larger diameter than the core diameter. At this end the fiber is provided with a reflector designed to conduct rays entering outside the fiber towards an area where they can be absorbed without causing any damage. In the illustrated embodiment this area is surrounded by a heat-abducting device with cooling fins, but it is also mentioned that water cooling means may be included in this area for cooling off the generated heat. Also in this case the cooling is provided from the outside of the component.
A weakness in all of these methods that now have been described is the fact that the heat first must be absorbed by a metal surface and then conducted through the metal material to the cooled surface either this surface is cooled by means of air or by water.